Systems and methods for a robotic-assisted revision procedure

ABSTRACT

A method of performing a procedure includes preparing a subject, gaining access to a portion of the subject with a first instrument, removing a first portion of the portion of the subject with the first instrument, gaining access to the portion of the subject with a tracked instrument, moving the tracked instrument to a surface revealed by removal of at least the first portion from the portion of the subject, tracking the tracked instrument while moving at least the tracked instrument to the surface, and determining a representation of the surface based on the tracking the tracked instrument.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/923,192, filed Jul. 8, 2020, which is a continuation of U.S.application Ser. No. 15/649,416, filed Jul. 13, 2017, which claimspriority to and the benefit of U.S. Provisional Application No.62/363,037, filed Jul. 15, 2016, all of which are hereby incorporated byreference herein in their entireties.

BACKGROUND

The present disclosure is related to robotic assisted orthopedicsurgeries, and in particular, to robotic assisted revision surgeries.

Currently, surgeons perform revision surgeries, such as revision kneeand hip procedures manually. This manual surgery is not always accurate,is difficult to perform, and could result in greater bone loss thandesired, which lessens the strength and integrity of the bone. Thelimited access and occurrence of inaccurate cutting, removing of theimplant, and cementation of the implant can cause significant bone loss.During the procedure, surgeons may use a chisel and micro saw tomanually dissect the implant. The surgeon has to perform this approachvery slowly in order to preserve the bone. The timing of the surgery,however, may be critical for the patient due to duration of theanesthesia. In addition, performing such a procedure requiressignificant training.

SUMMARY OF THE INVENTION

According to one exemplary embodiment, there is a method for performinga revision surgery using a robotic-assisted surgery system. The methodincludes determining, by a processing circuit associated with acomputer, information related to an interface area between an implantcomponent and a bone on which the implant component is implanted. Themethod further includes generating, by the processing circuit, a plannedvirtual boundary in a representation of the implant component and thebone, the planned virtual boundary associated with a portion of theinterface area to be removed, and based at least in part on theinformation related to the interface area. The method further includestracking, by a navigation system associated with the computer, movementin the physical space of a cutting tool such that movement of thecutting tool is correlated with movement of a virtual tool, andproviding a constraint on the cutting tool while the cutting toolremoves the portion of the interface area, the constraint based on arelationship between the virtual tool and the planned virtual boundary.The portion of the interface area is removed to remove the implantcomponent from the bone.

In some embodiments, determining information related to an interfacearea comprises receiving images of the bone and the implant componentimplanted thereon. In some embodiments, the images were obtained inrelation to a primary procedure during which the implant component wasimplanted on the bone. In some embodiments, the images are received byat least one imaging modality from a group consisting of: CT, x-ray,fluoroscope, MRI, ultrasound, video camera, and tracked markers. In someembodiments, determining information related to an interface areacomprises digitizing the interface area with a tracked probe.

In some embodiments, the method further includes receiving an input foradjusting the virtual boundary relative to the representation of theimplant and the bone. In some embodiments, the virtual boundary is ahaptic boundary and wherein providing the constraint comprises providinghaptic feedback to the cutting tool. In some embodiments, the virtualboundary is an autonomous control boundary and wherein providing theconstraint comprises autonomously controlling the surgical tool toremain within the control boundary. In some embodiments, the cuttingtool is one or more tools from the group consisting of but not limitedto: a planar saw, a curved saw, a laser, waterjet, ultrasoundvibrations, and a burr.

In some embodiments, the method further includes determining, by theprocessing circuit, information related to at least one of a size, aquantity, and a location of bone defects near the interface whichrequire an augment. In some embodiments, the information is determinedpre-operatively. In some embodiments, the information is determined bydigitizing the bone defects with a tracked probe.

In some embodiments, the method further includes using a video camera toobtain an image of the bone after the implant component has beenremoved; and generating a bone model of the bone based on the image forplanning replacement of the implant component.

In some embodiments, the method further includes determining a desiredpose of a replacement implant component to be implanted on the bone. Insome embodiments, the method further includes determining, by theprocessing circuit, a second planned virtual boundary in arepresentation of the bone representing one or more cuts in the bone toprepare the bone to receive the replacement implant. In someembodiments, the method further includes providing a constraint on thecutting tool while the cutting tool performs the one or more cuts toprepare the bone, the constraint based on a relationship between thevirtual tool and the second planned virtual boundary.

In another exemplary embodiment there is a system for performingrevision surgery. The system includes a robotic system comprising anarticulated arm and a surgical tool coupled to the articulated arm, anavigation system configured to characterize movement of at least one ofthe articulated arm, the surgical tool, and a portion of the patient'sanatomy for revision, and a processor operatively coupled to the roboticsystem and the navigation system. The processor is configured todetermine information related to an interface area between an implantcomponent and a bone on which the implant component is implantedgenerate a planned virtual boundary based upon a representation of theimplant component and the bone, the planned virtual boundary associatedwith a portion of the interface area to be removed, and based at leastin part on the information related to the interface area; track, usingthe navigation system, movement in the physical space of the cuttingtool such that movement of the cutting tool is correlated with movementof a virtual tool; and provide a constraint on the cutting tool whilethe cutting tool removes the portion of the interface area, theconstraint based on a relationship between the virtual tool and theplanned virtual boundary.

In some embodiments, the system further includes an imaging systemoperatively coupled to the processor for determining the informationrelated to the interface area, wherein the imaging system comprises atleast one of the imaging modalities from the group consisting of: CT,x-ray, fluoroscope, MM, ultrasound, video camera, and tracked markers.In some embodiments, the system further includes a tracked probe fordigitizing the interface area.

In some embodiments, the surgical tool coupled to the articulated armcomprises an end effector. The end effector includes at least oneflexible bending element capable of movement in two degrees of freedom,the bending element comprising a distal end, a proximal end and aninternal channel; a shaft coupled to the proximal end of the flexiblebending element and configured to secure the end effector to a surgicalsystem; and a motor housed in the shaft and coupled to the cutting toolto provide power to the cutting tool. A cutting element is coupled tothe distal end of the flexible bending element.

In an embodiment, a robotic system is used to assist in a knee or hiprevision procedure. The robotic system may include a navigation systemto register real bone to pre-scan CT images and precisely guide a robotarm to navigate through the patient anatomical space. The robotic systemmay have haptic capability, wherein the user can shape the haptic volumebased on patient anatomy to protect the important bone structure andsoft tissues (such as ligaments, nerves, and veins). The system mayfurther include a flexible end effector, having multiple degrees offreedom and can be bent 90 degrees in any direction to allow the cuttingtool, attached to the flexible arm, to access small area to dissect thebone implant. The system may have a large database which saves patientbone models and implant models and planning history during their primaryknee or hip procedure, with the information being available for use inrevision cases.

In another embodiment, the robotic system, using patient'sprevious/primary knee and hip information, can assist in revision casesby using a patient's previous/primary knee and hip implant model tocreate a revision haptic boundary to haptically guide the revisionprocedure; using a patient's previous/primary knee and hip bone model toregister the bone to robot coordinate, wherein the patient does not needto take an extra CT image for the revision case; and using patient'sprevious/primary knee and hip planning information to identify therelative position between bone and implant in the revision case, whereinthere is no relative motion between bone and implant, the implantsurface is used to register the bone to robot coordinate.

In some embodiments, the robotic system creates a customized revisionhaptic boundary to protect overcutting of the bone and minimizing thebone lost during the revision procedure.

In some embodiments, the robotic system, based on the primary knee andhip implant model, precisely creates the revision haptic boundary aroundthe primary implant to constraint the cutting tool and minimizeovercutting the bone. In some embodiments, one of the following methodsis used to register the implant and bone to primary knee and hip CTimage during the revision: a trackable probe to digitize the implantsurface and then register the bone to primary CT image; taking a fewfluoroscopic images; and/or attaching a camera or optical sensor to therobot to scan the implant surface and then register it to the primary CTbone model. In some embodiments, the robotic system includes a dexterousflexible end effector system, the flexible end effector having multipledegrees of freedom and bendable in omni-direction to allow robot cutbone with constraint access space, and the flexible end effectorcarrying a high-speed rotating burr for cutting bone. In someembodiments, a video camera or ultrasound device is used to create aninitial bone or implant model and/or to register the bone with the bonemodel.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated and constitute a partof this specification, illustrate several embodiments that, togetherwith the description, serve to explain the principles and features ofthe present disclosure.

FIG. 1 illustrates a perspective view of an embodiment of a surgicalsystem, according to an exemplary embodiment.

FIG. 2 illustrates a block diagram of a computing system according to anexemplary embodiment.

FIGS. 3A-3B illustrate an X-ray showing a femur, a tibia, a femoralimplant and a tibia implant, according to an exemplary embodiment.

FIG. 4 illustrates a bone model and implant model as shown on a userinterface during a primary partial knee procedure.

FIG. 5A illustrates a flexible end effector used with the surgicalsystem of FIG. 1, according to an exemplary embodiment.

FIG. 5B illustrates the flexible end effector of FIG. 5A, according toan exemplary embodiment.

FIG. 5C illustrates a close up view of a flexible portion of theflexible end effector of FIG. 5A, according to an exemplary embodiment.

FIGS. 6A-6C illustrate various views of a femur, a femoral implant andan end effector, according to an exemplary embodiment.

FIGS. 7A and 7B show a femoral implant and femur after non-robotic ormanual removal.

FIG. 8 is a flow chart of a method of performing a revision surgery,according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the application isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

The present disclosure introduces a robotic assisted approach to supporta revision procedure of a joint, such as the knee joint or the hipjoint, by allowing precise removal of a primary implant with minimalbone loss and while reducing the time needed to remove the primaryimplant. When bone loss is minimized, the number of revision proceduresthat may be performed on an individual patient during their lifetimeincreases.

Though the present disclosure makes reference to the knee and the hipjoint, and revisions for the knee and the hip, the systems and methodsdisclosed herein are equally applicable to other orthopedic revisionsurgeries for other bones or joints, including, but not limited to, theshoulder, the wrist, the ankle, the spine, etc.

The robotic-assisted surgery system of the present disclosure isdesigned to assist revision procedures to minimize the amount of boneremoved and/or the damage on the bone. The robotic assisted surgerysystem is also designed to shorten the lengthy learning curve for thesurgeon for performing a revision procedure. The robotic assistedsurgery system may help in reducing the time to perform a revision, andallow a better recovery of the bone because the bone may be less“damaged” as a result of the use of the robotic system. In addition, thedisclosure addresses one major issue of the previously used systemswhich is visibility of the progress of the breakdown of the interface.In certain embodiments, the robotic system can provide the user with aplan to remove the interface entirely, and then help the user executethe plan while providing feedback during the removal process.

Exemplary Robotic System

Various features of a robotic assisted surgery system and methodsaccording to the present disclosure will now be described in greaterdetail. FIG. 1 provides a schematic diagram of an exemplarycomputer-assisted surgery (CAS) system 100, in which processes andfeatures associated with certain disclosed embodiments may beimplemented. Surgical system 100 may be configured to perform a widevariety of orthopedic surgical procedures such as, for example, kneerevision procedures. Surgical system 100 includes a tracking system 101,computing system 102, one or more display devices 103 a, 103 b, and arobotic system 104. It should be appreciated that system 100, as well asthe methods and processes described herein, may be applicable to manydifferent types of joint revision procedures. Although certain disclosedembodiments may be described with respect to knee revision procedures,the concepts and methods described herein may be applicable to othertypes of orthopedic surgeries, such as hip revisions, shoulder revisionprocedures, and other types of orthopedic procedures. Further, surgicalsystem 100 may include additional elements or fewer elements than thosedescribed, to aid in surgery (e.g., surgical bed, etc.).

Robotic system 104 can be used in an interactive manner by a surgeon toperform a surgical procedure, such as a revision procedure, on apatient. As shown in FIG. 1, robotic system 104 includes a base 105, anarticulated arm 106, a force system (not shown), and a controller (notshown). A surgical tool 110 (e.g., an end effector having an operatingmember, such as a saw, reamer, or burr) may be coupled to thearticulated arm 106. The surgeon can manipulate the surgical tool 110 bygrasping and manually moving the articulated arm 106 and/or the surgicaltool 110.

The force system and controller are configured to provide a cuttingrestraint guide via control or guidance to the surgeon duringmanipulation of the surgical tool. The force system is configured toprovide at least some force to the surgical tool via the articulated arm106, and the controller is programmed to generate control signals forcontrolling the force system. In one embodiment, the force systemincludes actuators and a back-driveable transmission that provide haptic(or force) feedback to constrain or inhibit the surgeon from manuallymoving the surgical tool beyond predefined haptic boundaries defined byhaptic objects as described, for example, in U.S. Pat. No. 8,010,180and/or U.S. patent application Ser. No. 12/654,519 (U.S. PatentApplication Pub. No. 2010/0170362), filed Dec. 22, 2009, each of whichis hereby incorporated by reference herein in its entirety. The forcesystem and controller may be housed within the robotic system 104. Insome embodiments, cutting restraint or guidance is provided though ahandheld manipulator or handheld robotic device, such as described inU.S. Pat. No. 9,399,298 entitled “Apparatus and Method for Providing anAdjustable Positive Stop in Space,” U.S. Pat. No. 9,060,794 entitled“System and Method for Robotic Surgery,” and U.S. Patent Publication No.2013/0060278 entitled “Surgical instrument including housing, a cuttingaccessory that extends from the housing and actuators that establish theposition of the cutting accessory relative to the housing,” each ofwhich is incorporated herein by reference in its entirety.

Tracking system 101 is configured to determine a pose (i.e., positionand orientation) of one or more objects during a surgical procedure todetect movement of the object(s). For example, the tracking system 101may include a detection device that obtains a pose of an object withrespect to a coordinate frame of reference of the detection device. Asthe object moves in the coordinate frame of reference, the detectiondevice tracks the pose of the object to detect (or enables the surgicalsystem 100 to determine) movement of the object. As a result, thecomputing system 102 can capture data in response to movement of thetracked object or objects. Tracked objects may include, for example,tools/instruments, patient anatomy, implants/prosthetic devices, andcomponents of the surgical system 100. Using pose data from the trackingsystem 101, the surgical system 100 is also able to register (or map orassociate) coordinates in one space to those in another to achievespatial alignment or correspondence (e.g., using a coordinatetransformation process as is well known). Objects in physical space maybe registered to any suitable coordinate system, such as a coordinatesystem being used by a process running on a surgical controller and/orthe computer device of the robotic system 104. For example, utilizingpose data from the tracking system 101, the surgical system 100 is ableto associate the physical anatomy, such as the patient's tibia, with arepresentation of the anatomy (such as an image displayed on the displaydevice 103). Based on tracked object and registration data, the surgicalsystem 100 may determine, for example, a spatial relationship betweenthe image of the anatomy and the relevant anatomy.

Registration may include any known registration technique, such as, forexample, image-to-image registration (e.g., monomodal registration whereimages of the same type or modality, such as fluoroscopic images or MRimages, are registered and/or multimodal registration where images ofdifferent types or modalities, such as MM and CT, are registered),image-to-physical space registration (e.g., image-to-patientregistration where a digital data set of a patient's anatomy obtained byconventional imaging techniques is registered with the patient's actualanatomy), combined image-to-image and image-to-physical-spaceregistration (e.g., registration of preoperative CT and MM images to anintraoperative scene), and/or registration using a video camera orultrasound. The computing system 102 may also include a coordinatetransform process for mapping (or transforming) coordinates in one spaceto those in another to achieve spatial alignment or correspondence. Forexample, the surgical system 100 may use the coordinate transformprocess to map positions of tracked objects (e.g., patient anatomy,etc.) into a coordinate system used by a process running on the computerof the haptic device and/or a surgical controller. As is well known, thecoordinate transform process may include any suitable transformationtechnique, such as, for example, rigid-body transformation, non-rigidtransformation, affine transformation, and the like. In someembodiments, the video camera includes a tracker and a scan of the boneto obtain a model and register the model. For example, an initial 3Dmodel can be created and automatically registered. In some embodiments,the video camera can be used to register a 3D model corresponding to aCT scan. According to some embodiments, a video camera or ultrasound canbe used for both initial model creation and registration.

The tracking system 101 may be any tracking system that enables thesurgical system 100 to continually determine (or track) a pose of therelevant anatomy of the patient. For example, the tracking system 101may include a non-mechanical tracking system, a mechanical trackingsystem, or any combination of non-mechanical and mechanical trackingsystems suitable for use in a surgical environment. The non-mechanicaltracking system may include an optical (or visual), magnetic, radio, oracoustic tracking system. Such systems typically include a detectiondevice adapted to locate in predefined coordinate space speciallyrecognizable trackable elements (or trackers) that are detectable by thedetection device and that are either configured to be attached to theobject to be tracked or are an inherent part of the object to betracked. For example, a trackable element may include an array ofmarkers having a unique geometric arrangement and a known geometricrelationship to the tracked object when the trackable element isattached to the tracked object. The known geometric relationship may be,for example, a predefined geometric relationship between the trackableelement and an endpoint and axis of the tracked object. Thus, thedetection device can recognize a particular tracked object, at least inpart, from the geometry of the markers (if unique), an orientation ofthe axis, and a location of the endpoint within a frame of referencededuced from positions of the markers.

The markers may include any known marker, such as, for example,extrinsic markers (or fiducials) and/or intrinsic features of thetracked object. Extrinsic markers are artificial objects that areattached to the patient (e.g., markers affixed to skin, markersimplanted in bone, stereotactic frames, etc.) and are designed to bevisible to and accurately detectable by the detection device. Intrinsicfeatures are salient and accurately locatable portions of the trackedobject that are sufficiently defined and identifiable to function asrecognizable markers (e.g., landmarks, outlines of anatomical structure,shapes, colors, or any other sufficiently recognizable visualindicator). The markers may be located using any suitable detectionmethod, such as, for example, optical, electromagnetic, radio, oracoustic methods as are well known. For example, an optical trackingsystem having a stationary stereo camera pair sensitive to infraredradiation may be used to track markers that emit infrared radiationeither actively (such as a light emitting diode or LED) or passively(such as a spherical marker with a surface that reflects infraredradiation). Similarly, a magnetic tracking system may include astationary field generator that emits a spatially varying magnetic fieldsensed by small coils integrated into the tracked object.

Computing system 102 may be communicatively coupled to tracking system101 and may be configured to receive tracking data from tracking system101. Based on the received tracking data, computing system 102 maydetermine the position and orientation associated with one or moreregistered features of the surgical environment, such as surgical tool110 or portions of the patient's anatomy. Computing system 102 may alsoinclude surgical planning and surgical assistance software that may beused by a surgeon or surgical support staff during the surgicalprocedure. For example, during a joint replacement procedure, computingsystem 102 may display images related to the surgical procedure on oneor both of the display devices 103 a, 103 b.

Computing system 102 (and/or one or more constituent components ofsurgical system 100) may include hardware and software for operation andcontrol of the surgical system 100. Such hardware and/or software isconfigured to enable the system 100 to perform the techniques describedherein.

FIG. 2 illustrates a block diagram of the computing system 102 accordingto an exemplary embodiment. The computing system 102 includes a surgicalcontroller 112, a display device 103 (e.g., display devices 103 a and103 b), and an input device 116.

The surgical controller 112 may be any known computing system but ispreferably a programmable, processor-based system. For example, thesurgical controller 112 may include a microprocessor, a hard drive,random access memory (RAM), read only memory (ROM), input/output (I/O)circuitry, and any other known computer component. The surgicalcontroller 112 is preferably adapted for use with various types ofstorage devices (persistent and removable), such as, for example, aportable drive, magnetic storage, solid state storage (e.g., a flashmemory card), optical storage, and/or network/Internet storage. Thesurgical controller 112 may comprise one or more computers, including,for example, a personal computer or a workstation operating under asuitable operating system and may include a graphical user interface(GUI).

Still referring to FIG. 2, in an exemplary embodiment, the surgicalcontroller 112 includes a processing circuit 120 having a processor 122and memory 124. Processor 122 can be implemented as a general purposeprocessor executing one or more computer programs to perform actions byoperating on input data and generating output. The processes and logicflows can also be performed by, and apparatus can also be implementedas, special purpose logic circuitry, e.g., an FPGA (field programmablegate array) or an ASIC (application specific integrated circuit), agroup of processing components, or other suitable electronic processingcomponents. Generally, a processor will receive instructions and datafrom a read only memory or a random access memory or both. Memory 124(e.g., memory, memory unit, storage device, etc.) comprises one or moredevices (e.g., RAM, ROM, Flash-memory, hard disk storage, etc.) forstoring data and/or computer code for completing or facilitating thevarious processes described in the present application. Memory 124 maybe or include volatile memory or non-volatile memory. Memory 124 mayinclude database components, object code components, script components,or any other type of information structure for supporting the variousactivities described in the present application. According to anexemplary embodiment, memory 124 is communicably connected to processor122 and includes computer code for executing one or more processesdescribed herein. The memory 124 may contain a variety of modules, eachcapable of storing data and/or computer code related to specific typesof functions. In one embodiment, memory 124 contains several modulesrelated to surgical procedures, such as a planning module 124 a, anavigation module 124 b, a registration module 124 c, and a roboticcontrol module 124 d.

Alternatively, or in addition, the program instructions can be encodedon an artificially generated propagated signal, e.g., amachine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus for execution by a data processing apparatus. A computerstorage medium can be, or be included in, a computer-readable storagedevice, a computer-readable storage substrate, a random or serial accessmemory array or device, or a combination of one or more of them.Moreover, while a computer storage medium is not a propagated signal, acomputer storage medium can be a source or destination of computerprogram instructions encoded in an artificially generated propagatedsignal. The computer storage medium can also be, or be included in, oneor more separate components or media (e.g., multiple CDs, disks, orother storage devices). Accordingly, the computer storage medium may betangible and non-transitory.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

Generally, a computer will also include, or be operatively coupled toreceive data from or transfer data to, or both, one or more mass storagedevices for storing data, e.g., magnetic, magneto optical disks, oroptical disks. However, a computer need not have such devices. Moreover,a computer can be embedded in another device, e.g., a mobile telephone,a tablet, a personal digital assistant (PDA), a mobile audio or videoplayer, a game console, a Global Positioning System (GPS) receiver, or aportable storage device (e.g., a universal serial bus (USB) flashdrive), to name just a few. Devices suitable for storing computerprogram instructions and data include all forms of non-volatile memory,media and memory devices, including by way of example semiconductormemory devices, e.g., EPROM, EEPROM, and flash memory devices; magneticdisks, e.g., internal hard disks or removable disks; magneto opticaldisks; and CD ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an embodiment of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network.

Referring to the embodiment of surgical system 100 depicted in FIG. 2,the surgical controller 112 further includes a communication interface130. The communication interface 130 of the computing system 102 iscoupled to a computing device (not shown) of the robotic system 104 viaan interface and to the tracking system 101 via an interface. Theinterfaces can include a physical interface and a software interface.The physical interface of the communication interface 130 can be orinclude wired or wireless interfaces (e.g., jacks, antennas,transmitters, receivers, transceivers, wire terminals, etc.) forconducting data communications with external sources via a directconnection or a network connection (e.g., an Internet connection, a LAN,WAN, or WLAN connection, etc.). The software interface may be residenton the surgical controller 112, the computing device (not shown) of therobotic system 104, and/or the tracking system 101. In some embodiments,the surgical controller 112 and the computing device (not shown) are thesame computing device. The software may also operate on a remote server,housed in the same building as the surgical system 100, or at anexternal server site.

Computing system 102 also includes display device 103. The displaydevice 103 is a visual interface between the computing system 102 andthe user. The display device 103 is connected to the surgical controller112 and may be any device suitable for displaying text, images,graphics, and/or other visual output. For example, the display device103 may include a standard display screen, a touch screen, a wearabledisplay (e.g., eyewear such as glasses or goggles), a projectiondisplay, a head-mounted display, a holographic display, and/or any othervisual output device. The display device 103 may be disposed on or nearthe surgical controller 112 (e.g., on the cart as shown in FIG. 1) ormay be remote from the surgical controller 112 (e.g., mounted on a standwith the tracking system 101). The display device 103 is preferablyadjustable so that the user can position/reposition the display device103 as needed during a surgical procedure. For example, the displaydevice 103 may be disposed on an adjustable arm (not shown) or to anyother location well-suited for ease of viewing by the user. As shown inFIG. 1 there may be more than one display device 103 in the surgicalsystem 100.

The display device 103 may be used to display any information useful fora medical procedure, such as, for example, images of anatomy generatedfrom an image data set obtained using conventional imaging techniques,graphical models (e.g., CAD models of implants, instruments, anatomy,etc.), graphical representations of a tracked object (e.g., anatomy,tools, implants, etc.), constraint data (e.g., axes, articular surfaces,etc.), representations of implant components, digital or video images,registration information, calibration information, patient data, userdata, measurement data, software menus, selection buttons, statusinformation, and the like.

In addition to the display device 103, the computing system 102 mayinclude an acoustic device (not shown) for providing audible feedback tothe user. The acoustic device is connected to the surgical controller112 and may be any known device for producing sound. For example, theacoustic device may comprise speakers and a sound card, a motherboardwith integrated audio support, and/or an external sound controller. Inoperation, the acoustic device may be adapted to convey information tothe user. For example, the surgical controller 112 may be programmed tosignal the acoustic device to produce a sound, such as a voicesynthesized verbal indication “DONE,” to indicate that a step of asurgical procedure is complete. Similarly, the acoustic device may beused to alert the user to a sensitive condition, such as producing atone to indicate that a surgical cutting tool is nearing a criticalportion of soft tissue or is approaching a virtual control boundary.

To provide for other interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving input device 116 that enables the user to communicate with thesurgical system 100. The input device 116 is connected to the surgicalcontroller 112 and may include any device enabling a user to provideinput to a computer. For example, the input device 116 can be a knowninput device, such as a keyboard, a mouse, a trackball, a touch screen,a touch pad, voice recognition hardware, dials, switches, buttons, atrackable probe, a foot pedal, a remote control device, a scanner, acamera, a microphone, and/or a joystick. For example, input device 116can allow the user manipulate a virtual control boundary. Other kinds ofdevices can be used to provide for interaction with a user as well, forexample, feedback provided to the user can be any form of sensoryfeedback, e.g., visual feedback, auditory feedback, or tactile feedback,and input from the user can be received in any form, including acoustic,speech, or tactile input. In addition, a computer can interact with auser by sending documents to and receiving documents from a device thatis used by the user, for example, by sending web pages to a web browseron a user's client device in response to requests received from the webbrowser.

General surgical planning and navigation to carry out the exemplarymethods described above, and including haptic control and feedback asdescribed in connection with surgical system 100, may be performed by acomputerized surgical system such as that described in U.S. Pat. No.8,010,180 “Haptic Guidance System and Method” to Quaid et al., which isincorporated herein by reference in its entirety.

Virtual Objects for Robotic Assisted Surgery

FIGS. 3A-3B illustrate an example x-ray showing a femur (F), a tibia(T), a femoral implant 302 and a tibial implant 306, according to anexemplary embodiment. While an x-ray image is shown in FIGS. 3A and 3B,other images can be acquired and used to generate bone models using anyof a variety of imaging techniques (e.g., CT, MM, ultrasound, videocamera, etc.) As shown, the femoral implant 302 includes projections,such as a peg 304 extending into the femur F, and the tibial implant 306includes, for example, a keel 308. During implantation, cement isprovided under flat portions of a baseplate of the tibial implant 306and along flat surfaces of the femoral implant 302. In some embodiments,the femoral implant 302 includes 5 flat portions, portion ab, portionbc, portion cd, portion de, and portion ef. In some embodiments, cementis located on some or all of the flat portions of the femoral implant302. During a revision surgery, the implants 302 and 306 must be cutaround for removal, including the peg 304 and the keel 308. However,over time, the keel 308 may have ingrowth with the tibia T that maycause bone pieces to break off during removal. To reduce the bone lossduring removal, an image of the implant (e.g., obtained by CT, Mill,video, ultrasound, etc.), can be used to create a model of the bones andthe implants for generation of surgical plans for removal. In someembodiments, a tracking probe can be used to probe, for example, areasnear points a, b, c, d, e and f or along the edges of portions ab, bc,cd, de and ef to generate a model of the interface between the femoralimplant 302 and the bone.

FIG. 4 illustrates a graphical user interface showing a model of a bone402 and a model of an implant 404 during a primary partial kneeprocedure, according to an exemplary embodiment. Specifically, FIG. 4depicts a distal end of a femur 402 that received the femoral implant404. As shown, the femoral implant 404 includes elongated projections406 (e.g., pegs, screws, keels, etc.) that were received by apertures inthe femur. The elongated projections 406 further secure the femoralimplant 404 to the bone 402 and help resist movement between the implant404 and the bone 402. The bone may have been prepared with keels (notshown), which interface with keels on the femoral implant 404 to improvesecurity between the bone 402 and the implant 404. The model may allow auser to modify the view of the implant model through rotation of themodel or selection of different viewing modes. In some embodiments, themodel may allow a user to view different cross sectional views of theimplant, bone, or a combination thereof. In some embodiments, the modelmay also provide information to aid in planning a revision surgery(e.g., size, location, material, etc.).

The surgical system 100 of FIG. 1 may be configured to establish avirtual control object associated with the current prosthetic implantcomponent and associated with or relative to one or more features of apatient's anatomy. The surgical system 100 may be configured to create avirtual representation of a surgical site that includes, for example,virtual representations of a patient's anatomy, a surgical instrument tobe used during a surgical procedure, a probe tool for registering otherobjects within the surgical site, and any other object associated with asurgical site.

In addition to physical objects, the surgical system 100 may beconfigured to generate virtual objects that exist in software and may beuseful during the performance of a surgical procedure. For example,surgical system 100 may be configured to generate virtual boundaries orvirtual control boundaries, that correspond to a surgeon's plan forpreparing a bone, such as boundaries defining areas of the bone that thesurgeon plans to cut, remove, or otherwise alter. In the case of arevision surgery, the virtual boundaries may correspond to a surgeon'splan for removing the cement and the necessary bone making up theinterface between an implanted prosthetic component and the bone onwhich it is implanted. Alternatively, or additionally, surgical system100 may define virtual objects that correspond to a desired path orcourse over which a portion of surgical tool 110 (e.g., end effector200) should navigate to perform a particular task.

The surgical system 100 may also be configured to generate virtualobjects or boundaries as part of a specific surgical plan. In someembodiments, the surgical plan is generated based on a database ofimplants where the surgical plans correspond to registered models ofimplants or bones. If an implant is known in the database, a surgicalplan can be proposed to the user. The surgical plan may include whichtools should be used, what access is needed to get around parts of theimplant, virtual boundaries, etc. The proposed surgical plan may includevirtual objects around keels and pegs, and may propose tool changes forcutting around these implant features. In some embodiments, the surgicalplans are modifiable by the user including, but not limited to, thetools to be used, the access needed, the shape of the implant and thevirtual boundaries. In some embodiments, a generic surgical plan can beautomatically modified based on a model capture of the patient's anatomyor implant, or on the specific implant.

Virtual boundaries and other virtual objects may define a point, line,or surface within a virtual coordinate space (typically defined relativeto an anatomy of a patient) that serves as a boundary at which aconstraint is provided to a surgical instrument when the trackedposition of the surgical instrument interacts with the virtual boundaryor object. In some embodiments, the constraint is provided throughhaptic or force feedback. For example, as the surgeon performs a bonecutting operation, a tracking system of the surgical system 100 tracksthe location of the cutting tool and, in most cases, allows the surgeonto freely move the tool in the workspace. However, when the tool is inproximity to a virtual boundary (that has been registered to the anatomyof the patient), surgical system 100 controls the force feedback systemto provide guidance that tends to constrain the surgeon from penetratingthe virtual boundary with the cutting tool. For example, a virtualboundary may be associated with the geometry of a virtual model of aprosthetic implant, and the haptic guidance may comprise a force and/ortorque that is mapped to the virtual boundary and experienced by thesurgeon as resistance to constrain tool movement from penetrating thevirtual boundary. Thus, the surgeon may feel as if the cutting tool hasencountered a physical object, such as a wall. Accordingly, the forcefeedback system of the surgical system 100 communicates this informationto the surgeon regarding the location of the tool relative to thevirtual boundary, and provides physical force feedback to guide thecutting tool during the actual cutting process. In this manner, thevirtual boundary functions as a virtual cutting guide. The forcefeedback system of the surgical system 100 may also be configured tolimit the user's ability to manipulate the surgical tool. The roboticsystem or manual tools could be attached to the implant to measure anapplied force for removal. Monitoring the position of the implant withrespect to the bone and the force applied could give the surgeon anindication of the ease of removal. This may indicate additional cuttingis required to minimize unintentional bone loss. In some embodiments,the virtual boundaries define autonomous cutting controls allowing asurgical robot to perform all or some of the steps of the surgical planautonomously. In some embodiments, the virtual boundaries define acombination of autonomous and manual cutting boundaries. In someembodiments, when using autonomous cutting controls, feedback can beused to indicate contact is made with the implant (e.g., contact madewith a peg when the tool is cutting along a flat interface surface) andthe surgical plan or boundaries could be adjusted to avoid the portionof the implant based on the feedback. For example, this may beparticularly useful where a shape of a keel is not known or identifiableprior to beginning cutting, so the original boundaries do not take thekeel into account. A surgical plan or virtual boundaries could bemodified based on detected differences in the surgical plan and/orvirtual boundary and the keel. In some embodiments, the virtualboundaries correspond to haptic boundaries defining a haptic object. Insome embodiments, the haptic boundary is configured to provide hapticfeedback when the haptic boundary is encountered. The haptic boundarycan result in haptic feedback that is tactile, audible, visual,olfactory (i.e., smell), or other mean of providing feedback.

In some embodiments, the rendering application also creates a virtualobject (not shown) that represents a pathway from a first position to asecond position. For example, the virtual object may include a virtualguide wire (e.g., a line) defining a pathway from a first position(e.g., a position of a tool in physical space used with the surgicalsystem 100) to a second position that includes a target (e.g., a targetobject such as the virtual object). The virtual object may be activatedso that movement of the tool is constrained along the pathway defined bythe virtual object. The surgical system 100 may deactivate the objectwhen the tool reaches the second position and activates the targetobject (e.g., the virtual object). The tool may be automatically placedin a control, such as haptic control, (or burring) mode when theobjectis activated. In a preferred embodiment, the object may bedeactivated to enable the tool to deviate from the pathway. Thus, theuser can override the guidance associated with the object to deviatefrom the guide wire path and maneuver the tool around untracked objects(e.g., screws, retractors, lamps, etc.) that may not be accounted forwhen the virtual guide wire is generated.

In the control mode, the robotic system 104 is configured to provideguidance to the user during a surgical activity such as bonepreparation. In one embodiment, the rendering application may includethe virtual object defining a cutting volume on the tibia T. The virtualobject may have a shape that substantially corresponds to a shape of asurface of a tibial component such as when preparing for implantation.In revision surgery, the virtual object may have a shape thatsubstantially corresponds to a shape of the interface between, forexample, the tibial component and the tibia on which it is implanted orthe path for bone removal to be followed. The robotic system 104 mayenter the control mode automatically, for example, when the tip of thetool approaches a predefined point related to a feature of interest. Insome embodiments, the tool can be disabled whenever the tool is outsidethe virtual object. In another embodiment, the tool can be disabledunless the robotic system 104 is generating control feedback forces.

In operation, the surgical system 100 may be used for surgical planningand navigation. In addition to preparing a revision surgery, thesurgical system 100 may be used, for example, to perform a kneereplacement procedure or other joint replacement procedure involvinginstallation of an implant. The implant may include any implant orprosthetic device, such as, for example, a total knee implant; aunicondylar knee implant; a modular knee implant; implants for otherjoints including hip, shoulder, elbow, wrist, ankle, and spine; and/orany other orthopedic and/or musculoskeletal implant, including implantsof conventional materials and more exotic implants, such asorthobiologics, drug delivery implants, and cell delivery implants.

Robotic Revision Surgery

Revision surgery, such as knee revision, is a complex procedure andrequires a very high level of expertise. There are several reasons thatmake the procedure more complex. The surgeon has to remove the originalimplant, which may be cemented or uncemented. The implant could havebone grown into it, and while removing the original implant, the surgeonhas to try and conserve as much bone as possible. Furthermore, theimplant(s) may include surfaces, keels, pegs, screws, or othercomponents that need to be cut around, or through. In some embodiments,the implant may be multiple implants that individually need to be cutaround and removed. Surgeons have to ensure that most of the bondsbetween the cement and the bone and/or between the implant and the boneare broken, resulting in a time consuming and complex process.Pre-existing solutions requires surgeons to chip away at the interfaceof bone-implant or bone-cement with manual or powered instruments. Theseinclude osteotomes, gigli saws and punches. Powered instrumentation isalso available, for example power saws and burrs or ultrasonic devices.Despite attempts to preserve bone, there is always some amount of boneloss, and the surgeon must accurately fill in all the bone defects dueto bone loss during removal of the implant. There may also bepre-existing bone defects that require attention after removal of theimplant. The robotic system and specialized instrumentation of thepresent disclosure can help to resolve some of the issues faced duringexplantation.

The need for a revision can include, for example, infections,misalignment, and wear. In knee revision due to infection, the surgerymay be a two stage surgery. In the first stage, the infected implant isremoved, and the wound is cleaned. A spacer block is added to the jointand the wound is closed. The second stage removes the spacer and addsthe new revision implant.

The present disclosure addresses the previously-faced issues of kneeand/or hip revision by using a robotic-assisted approach. The presentdisclosure also describes a flexible end effector carrying a high-speedcutting burr. The flexible end effector is very dexterous to allowaccess to small areas such as the tibia posterior surface to remove theimplant. Referring to FIGS. 5A-5C, a flexible end effector 200 which maybe used with the robotic arm 106 to perform a robotic assisted hip andknee revision procedure is shown, according to an exemplary embodiment.In some embodiments, the flexible end effector 200 may be an endeffector according to any of the embodiments described in U.S. patentapplication Ser. No. 15/436,460, which is herein incorporated byreference in its entirety.

Removing the implant manually can be difficult due to the limited accessto the curtain bone area, such as a tibia posterior surface. Theflexible end effector 200 is able to extend the robotic arm capabilityand allow access to those small areas. As shown in FIGS. 5A and 5B, theflexible end effector 200 includes two flexible bending elements 202 and204. Each element has two degrees of freedom and can be bent less orover 90 degrees in a three-dimensional space, as shown in FIG. 5C. Theend effector 200 may include a large internal channel to carry aflexible shaft. The flexible shaft is, for example, a hollow tube with asmall wall thickness and is capable of spinning a cutting burr. In someembodiments, the hollow tube is capable of spinning the cutting burr at60000 rpm. The flexible shaft's internal channel may also be used for anirrigation or suction channel. In some embodiments, the flexibleelements 202 and 204 provide increased access for areas that areotherwise difficult to reach.

The end effector 200 includes a housing 206 with a base 208 and a mount210. The base 208 secures the end effector 200 to the robotic arm 106and provides stability to the end effector 200. Mount 210 secures ashaft 212 of the end effector 200. The shaft 212 houses a motor 214 thatprovides power to a cutting tool 216 located at a distal end of the endeffector 200. In some embodiments, the end effector 200 also includes asuction hole 218. Suction hole 218 connects to the flexible shaft'sinternal channel. In some embodiments, the robotic arm 106 may be fixedand the end effector 200 may move autonomously to perform planned cuts,as described below.

A variety of cutting tools 216 could be selected for the type of bonecut to be completed. A saw could be used for a planar cut, a burr for acurved surface, a curved saw may be used to obtain access around pegs,keels and/or screws (can be cut around or cut through and removedseparately, or another cutting tool could be used that is better suitedfor the access to the bone and the type of cut to be created. A curvedtool, or a tool capable of performing a curved cut is preferred for thecritical posterior portions of the knee. In an exemplary embodiment, asaw could be used to perform initial cuts, and then more specific cutscould be performed using the specialized end effector 200. In someembodiments, ultrasonic tools can be used to vibrate and break up bonecement for removal. In some embodiments, a laser can be used to meltcement. In some embodiments, a waterjet can be used to cut or break upcement.

FIGS. 6A-6C illustrate various views of a femur F, a femoral implant 302and another exemplary embodiment of an end effector 200. End effector200 in FIGS. 6A-6C may include a base 208, a mount 210 and a cuttingtool 216. The end effector 200 may be a vibratory chisel. In someembodiments, the cutting tool is capable of chipping and cutting awaycement between bone and implant. The end effector 200 may be controlledand advanced by the surgeon, but may be constrained by a haptic boundarylocated between the bone and the implant to reduce skiving effect andensure that all of the cement attachment would be accessed to preserveas much bone as possible. The end effector 200 may be used during therevision surgery to remove the implant by cutting along portions ab, bc,cd, de, and ef. The end effector can further by used to prepare the bonefor a new implant. The bone may be prepared by creating surfaces ab, bc,cd, de, and ef in addition to a peg hole 310 for receiving peg 304 usingcutting tool 216 or a variety of other cutting tools.

FIGS. 7A and 7B show a femoral implant 302 after removal from a femur,when the removal is performed manually or without the use of a roboticsystem. As can be seen in the figures, in some revision surgeries,excess bone is removed when the implant 302 is removed, shown as bone312 remaining on the implant 302. When excess bone is removed, unevensurfaces 314 are created on the bone. Often, the excess bone removaloccurs directly around a keel, peg or on the back side of the implantwhere it is difficult to cut the cement. In order to properly preparethe bone for a new implant, defects may need to be filled usingaugments, cones, or other filling methods. Video or ultrasoundtechniques may be used after removal of the implant to determine thecharacteristics of the remaining bone, to assist with correction ofdefects and planning re-implantation.

The surgeon may execute the revision procedure using a robotic system toaid the surgeon in removal of the primary implant using various methods,described below.

FIG. 8 is a flow chart of a method 800 of performing a revision surgery,according to an exemplary embodiment. Before beginning the procedure,information related to an interface area between an implanted implantcomponent and the bone on which it is implanted must be obtained. Thiscan be accomplished using images of the revision site or using othertools to understand the relationship other than by images. Thesevariations for obtaining the interface information, depicted by optionalsteps 802, 804, and 806 in FIG. 8, are described below.

A first exemplary embodiment of the revision surgery method utilizesimages of the patient's anatomy to plan the revision. When a patient'sprimary case (e.g., initial surgery) is performed by a robotic-assistedsystem, the bone model and implant information may already be availableand there is no need to recapture images to perform a revision. At thetime of the revision surgery, the patient's primary knee and hip bonemodel and implant information are available for the robotic assistedsystem, as depicted in FIG. 4. In addition, models of the implant may beknown and stored in a library of the surgical system for use duringplanning.

In other cases, patient imaging data may not be available or it isdesired to obtain new images. Accordingly, initial or new scans must beperformed before planning and executing the revision procedure. In suchembodiments, as shown by optional step 802, the patient's anatomy isimaged using any preferred imaging modality, such as a CT or MRI scan,fluoroscopy, ultrasound, tracked markers, or by using a video camera.The images captured by the imaging device are used to create bone andimplant models for use in the planning stages. (In some embodiments, ina case of a two stage revision, imaging can also be done after a spacerblock is implanted. The spacer block may have features that will enableregistration of the spacer block during the implantation surgery.) Insome embodiments, a robotic device can be attached to an imaginingdevice for intraoperative registration and tracking. The scan is thensegmented or converted to bone models, at optional step 804. The scanmay be segmented in a predefined manner, or the surgeon may be able toselect segmentation parameters. In some embodiments, when using a videocamera, a 3D model can be created without segmentation. In someembodiments, a 3D model can be created using imaging, a statisticalmodel, etc. As described above, registration of the images to thephysical space/anatomy is executed by the surgical system 100.

In another exemplary embodiment, where image data is not captured on thepatient's anatomy or is not used, the method may capture dataintraoperatively with optional step 806. In this step, the perimeter ofthe cement to bone or implant to bone interface is digitized using atracked probe. Positional data of the tracked probe is captured by atracking system, such as tracking system 101 to determine the locationof the interface to be released. Digitizing the interface may also beperformed in addition to models when image data, bone models, and/orimplant models are available and/or used for the planning. The implantcan then be registered to the primary bone model. In yet anotherembodiment, a camera or optical sensor may be coupled to the robotic armto scan the implant surface and register it to the bone model. Inanother embodiment, a video camera can be moved around the patient toscan the bone and implant surface and create a 3D model. The surface ofthe implant can be probed to register the known implant location, orknown features of the implant. In some embodiments, if the implant isknown, probing can identify and register the implant with an implantmodel.

Planning the implant removal cuts is performed at step 808. In anembodiment where the image data is available from a pre-operative scan(whether it be recent scans or scans from the primary implantationsurgery), the removal cuts may be based upon the images and the locationof the interface between the cement and bone or the implant and bone. Insome embodiments, a video camera is used to define planes and virtualboundaries. In some embodiments, a probe can be used to define planesand virtual boundaries. Alternatively, the removal cuts may be based onthe intended replacement implant. In this way, the planned resectioncuts may be planned to properly accommodate the new implant while alsoremoving the current implant. In some embodiments, the planning softwaregenerates the bone preparation plan to achieve the right alignment forthe patient, such as a proper alignment of the tibia and femur.According to some embodiments, the robotic system 104 helps the surgeonplan and execute the right alignment for the knee in 3D. The bonepreparation plan may be carried out automatically by the planningsoftware, or the surgeon can aid in creating the bone preparation plan.Using previous image data (x-ray, CT, MM, fluroscopic, video, etc.) andintra-operative landmarks, a visualization of ideal native anatomy canbe constructed, such as joint line, etc. The system can use range ofmotion and soft tissue compliance as input to assist with planning theprocedure, as well. In some embodiments, fiducials may be placed in thespacer block to speed registration for the re-implantation surgery.After implant removal, the robot or manual tools could be used to removeremaining cement. Hand held tracked probes or probe attachments to therobot arm could be used to identify remaining cement in a 3D model. Themodel can be used to create another robotic cutting path for cementremoval.

In other embodiments, planning the implant removal cuts at step 808 canbe based on the data collected by the digitized probe. Typically, totalknee arthroscopy implant designs can include several flat bone facingsurfaces. During digitization, points on each side of the implant couldbe collected to identify the planar surfaces. Using the perimeter data,the robotic system calculates a plan to separate the interface ofinterest. Using a probe to collect points to define planes that can beused for virtual boundaries. Probing the transition areas of the implant(the points between two flat surfaces can help identify the virtualboundaries). Intra-operative imaging or the use of a video camera cancreate models of the bone defect after implant removal. Updates to theexisting model can be made by probing the defect to indicate where thereis additional bone loss. This defect model can be used in the revisionimplant planning to assure proper implant selection to cover the defect.The defect model indicates the need for additional augment devicesrequired to fill the defect. After the revision implants are selected,virtual boundaries are created for cutting the bone for implantinsertion. Once the models and defects are created, a new plan can begenerated to implement the modification and additions that need to bemade to bone due to bone loss to accommodate insertion of a new implant.

As part of this planning step 808, as described above, the surgicalsystem 100 generates a control object, such as a haptic object. Thecontrol object may define virtual boundaries that correspond to thesurgeon's plan for preparing a bone. In particular, for a revisionprocedure, the virtual boundary is associated with a portion of theinterface area that the surgeon plans to cut, remove, or otherwise alterin order to remove the current implant from the bone. A revision virtualboundary is created around the at least a portion of the interface areato allow the surgeon to precisely cut the bonding area between the boneand implant. In preferred embodiments, the virtual boundary for revisionis created adjacent to the implant surface to protect from overcuttingthe bone. In this way, the revision boundary will minimize the boneremoved, will reduce the risk of tear off the bone, and could increasethe number of potential additional revision procedures which could beoperated on patient in his/her lifetime. The boundary may be a planarboundary to which the cutting tool will be constrained by the virtualboundary, or a contoured boundary of any shape. The boundary may becreated automatically by the system based on that image and positionaldata received, or may be manually created based on user input. In otherembodiments, the boundary may be customizable or adjustable, forexample, a surgeon may choose to move the boundary closer or furtheraway from the interface to accommodate the quality of the bone. Usingthe control objects defining the virtual boundaries, the robotic systemcan ensure that the cutting tool does not migrate outside of a desiredcutting area, the minimal bone is removed, and that the cuts areexecuted accurately. If the implant is known, virtual boundaries can beidentified with a proposed surgical plan. The proposed surgical plan canbe used as a starting template for the surgeon that can be modified tofit specific needs and/or conditions of the operation. In someembodiments, the proposed plans are generic. In some embodiments, theproposed plans provide proposed tools and/or proposed access locationsfor preparing the bone for implant features, such as keels, pegs, or anyother structures or shapes that need to be avoided. In some embodiments,a generic template of shapes can be used in the virtual boundaryplanning or custom shapes can be drawn, created or selected during thesurgical planning. In particular, the surgical plan may need to becustomized based on the characteristics of the remaining bone after theinitial implant has been removed. In some embodiments, access locationsand dimensions can be identified in the proposed surgical plan. In someembodiments, entry paths can be outlined in the proposed surgical plan.

In some embodiments, the planning software can also determine the sizeand number of augments needed, at step 810. The planning software mayselect an augmentation size based on a database of information. Inanother embodiment, the planning software allows the user to enter thesize and number of augments needed. For example, a surgeon can tell thesystem, via the graphical user interface, to add a 5 mm posterioraugment or a medial 20 deg tibia wedge, and the planning software allowsfor such cuts to be executing by a surgical tool coupled to the roboticarm, instead of thru jigs. Pre-operative augment sizing and planning,made possible by using a robotic system according to the exemplaryembodiments disclosed herein, save valuable operating room time and makethe procedure more efficient and precise.

In step 812, the robotic system 104 tracks movement of the cutting tool,using the navigation system 101, and guides the surgeon while theplanned cuts are performed. The system 104 can guide the execution ofthe cuts by providing a constraint on the cutting tool based on arelationship between the virtual tool (associated with the cutting tool)and the virtual boundary. The guide can be provided using haptics or thesystem can autonomously perform the cuts, based on the control objectsgenerated by the system that correspond with the surgical plan. Whenhaptics are used, the surgeon will receive feedback indicating when ahaptic boundary is reached, preventing the surgeon from removingexcessive bone. In some embodiments, the surgeon can use a combinationof haptic control and autonomous action to perform the cuts. In someembodiments, the robotic system may also provide feedback related to thebone implant or bone cement breaking up process. For example, therobotic system may provide the surgeon with information on the progressof the cement bone or implant bone interface break. This may prevent anyunintentional loss of bone while pulling out the implant if theinterface is not yet properly broken.

In some embodiments, the robotic system 104 may remove hardware thruimpaction. The robotic system can use the force of robot arm to “jolt”implants loose or through use of the end effector acting like a woodpecker.

Use of a robotic system allows for use of a variety of cutting tools,based on the type of bone cut to be completed. A saw could be used for aplanar cut, a burr for a curved surface, a curved saw may be used toobtain access around pegs or keels, and/or access around or throughscrews or another cutting tool could be used that is better suited forthe access to the bone and the type of cut to be created. The roboticsystem tracks the cutting tools and the patient to monitor the cuttingprocedure and provide the user with information on the progress of thecement bone or implant bone interface break. Again, this reducesunintentional loss of bone that may occur while pulling out the implantprior to properly releasing the interface. In some embodiments, a value,such as a percentage, of the surface resection can be displayed. Thiscan give the surgeon an indication of the appropriate time to attemptimplant removal. In some embodiments, if the surgeon is concerned aboutbone loss in a specific area, the display could show an amount of boneremoval for a specific area of interest. In some embodiments, thesurgeon can identify the specific area of interest to be calculatedbefore or during surgery.

Furthermore, the robotic system or manual tools could be attached to theimplant to measure an applied force for removal. Monitoring the positionof the implant with respect to the bone and the force applied could givethe surgeon an indication of the ease of removal. This may indicate whenadditional cutting is required to minimize unintentional bone loss.

After implant removal, if there are any bone defects that the planningsoftware did not take into account, the bone defect may be digitized oridentified by another means at optional step 814. At step 816, theplanning software may generate the sizing information for filling thedefect with various implant or biomaterial fillers. The implants and/orbiomaterial fillers may be selected from a database of availableimplants or fillers. In some embodiments, the software can generateplans and create custom implants or fillers for filling the defect. Insome embodiments, the software selects implants and/or biomaterialfiller based on several factors (e.g., defect size, bone density, etc.).According to some embodiments, the robotic system 104 is able todetermine the correct size of cones used to fill defects. In otherembodiments, bone filler materials could be cut to the size of thedefect, or the system could be configured to inject liquid fillers intothe defect that could be solidified inside the patient.

In step 818, the planning software determines a desired pose of thereplacement implant in the bone, and plans bone preparation forreceiving the replacement implant. The planning may be carried out, andcontrol objects created, in a similar manner as described in step 808.There are several additional ways in which the robotic system can assistwith a revision procedure, in addition to executing those stepsdiscussed above. With respect to planning and preparing for implantationof a new implant component, the display device 103 may display limbalignment/balancing screens for an assessment of how implants areinstalled, which will help with planning the adjustment. Furthermore,the system may help assess stem length, straight vs. bowed, cemented vs.press-fit based on bone morphology, quality, and adjacent hardware, etc.The assessment may be patient specific or predictive from a pre-defineddata set. In another embodiment, the robotic system may applydistraction through a leg holder, spread, balancer, etc. to assess anddefine collateral tension. This can be performed at a plurality ofposes, and the graphical user interface or internal algorithm can beemployed to calculate joint line placement and component sizes to bestrestore kinematics and function. In yet another embodiment, the roboticsystem may be used to assist in revision surgeries from partial knee,bicompartmental, or tricompartmental into cruciate retaining, cruciatesubstituting, or posterior stabilized.

A video camera may also be used in step 814 to create a model of thebone after the implant has been removed. This identifies the currentbone geometry without the implant, including any bone defects thatrequire attention. The video camera and the images obtained therefromcan then be used in step 818 for planning the bone cuts, in step 820(described below) for executing the bone cuts to prepare the bone forthe replacement implant, and for placing the implant. In someembodiments, the video camera can be used during other phases of theprocedure, such as for model creation, registration, or tracking thepositions of the anatomy or the surgical tool(s) used during theprocedure. In some embodiments, the model may also includeidentification of the incisions, either by selecting the edge in thesystem software, using color identification, image detection ofretractors holding the incision open, or applying a material around theincision that can be detected by the camera. The video camera may thenalso be used to track the location of the incision during the procedure.

In step 820, the cuts for preparing the bone surface for placingaugments, cones, fillers, and the final implant are executed. Thesurgeon can perform the bone preparation cuts using guidance from thesystem such as haptic feedback. In another embodiment, the roboticsystem 104 may autonomously perform the preparation cuts. As describedabove, the system can resect the bone for the new plan as a step toremove the existing hardware. Therefore, instead of sawing/chipping awayat the existing implant, a resection is made that will help remove theimplant but also be the proper cuts for the next implant.

In some embodiments, the robotic system can be used in additional wayswhile performing cuts to the bone. For example, the system can assistwith executing adaptive cuts where subsequent cuts are made may be basedon a variety of possible inputs of prior cut data or otherlandmarks/objectives. For example, a probe may define the distal planeand posterior tangent for example and for a defined size implant makethe rest of the cuts (femur or tibia or patella). The input can be anexisting resection or a target articular tangency. The computed cuts canbe programmed based on inputs to create a desired outcome. In addition,the system can be used for cut refinement. A surface is probed and thenskim cut, (e.g., 0.5-1 mm cut). Control boundaries, such as haptics, canbe updated or generated intra-operatively as the cuts are made. Inanother example, the robotic system 104 can control saw performancebased on bone quality. Super soft/spongy bone or hard sclerotic bonemight need a “lighter” or “harder” touch in speeds and/or feeds, or evendifferent blades.

The robotic system can also assist with placement of the implant andassessment after the implant has been replaced. For example, the displaydevice showing a graphical user interface may be used to guide a surgeonon placement of the femoral or tibial components with stems, in terms ofthe offset or angled couplers or manipulating the anterior-posterior ormedial-lateral position slightly to achieve less tip or cortical stresspoints. Furthermore, the robotic arm can be used to hold the implant inplace relative to the bone while the cement is curing. In yet anotherembodiment, the system can help assess, via a range of motion/balancinggraphical user interface, if the new construct is stable enough.

In some embodiments, the robotic system 104 may visualize implant pathsor cement areas when considering other aspects of surgery, for examplewhen a tibia tuberosity is translated and the window of tibia sectionedand moved, where the hardware is, be it trauma plates, etc. relative toknee implants, etc.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, use of materials, colors, orientations, etc.). For example,the position of elements may be reversed or otherwise varied and thenature or number of discrete elements or positions may be altered orvaried. Accordingly, all such modifications are intended to be includedwithin the scope of the present disclosure. The order or sequence of anyprocess or method steps may be varied or re-sequenced according toalternative embodiments. Other substitutions, modifications, changes,and omissions may be made in the design, operating conditions andarrangement of the exemplary embodiments without departing from thescope of the present disclosure.

The present disclosure contemplates methods, systems and programproducts on any machine-readable media for accomplishing variousoperations. The embodiments of the present disclosure may be implementedusing existing computer processors, or by a special purpose computerprocessor for an appropriate system, incorporated for this or anotherpurpose, or by a hardwired system. Embodiments within the scope of thepresent disclosure include program products comprising machine-readablemedia for carrying or having machine-executable instructions or datastructures stored thereon. Such machine-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer or other machine with a processor. By way of example,such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROMor other optical disk storage, magnetic disk storage, other magneticstorage devices, solid state storage devices, or any other medium whichcan be used to carry or store desired program code in the form ofmachine-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer or othermachine with a processor. When information is transferred or providedover a network or another communications connection (either hardwired,wireless, or a combination of hardwired or wireless) to a machine, themachine properly views the connection as a machine-readable medium.Thus, any such connection is properly termed a machine-readable medium.Combinations of the above are also included within the scope ofmachine-readable media. Machine-executable instructions include, forexample, instructions and data which cause a general purpose computer,special purpose computer, or special purpose processing machines toperform a certain function or group of functions.

Although a specific order of method steps may be described, the order ofthe steps may differ from what is described. Also, two or more steps maybe performed concurrently or with partial concurrence. Such variationwill depend on the software and hardware systems chosen and on designerchoice. All such variations are within the scope of the disclosure.Likewise, software implementations could be accomplished with standardprogramming techniques with rule based logic and other logic toaccomplish any connection steps, processing steps, comparison steps, anddecision steps.

What is claimed is:
 1. A method of performing a procedure, comprising:preparing a subject; gaining access to a portion of the subject with afirst instrument; removing a first portion of the portion of the subjectwith the first instrument; gaining access to the portion of the subjectwith a tracked instrument; moving the tracked instrument to a surfacerevealed by removal of at least the first portion from the portion ofthe subject; tracking the tracked instrument while moving at least thetracked instrument to the surface; and determining a representation ofthe surface based on the tracking the tracked instrument.
 2. The methodof claim 1, further comprising predetermining a volume to remove fromthe subject prior to gaining access to the portion with the firstinstrument.
 3. The method of claim 1, wherein moving the trackedinstrument to the surface comprises contacting the surface with anon-cutting tip of the tracked instrument.
 4. The method of claim 1,wherein the first portion comprises a primary implant and bone coupledto the primary implant.
 5. The method of claim 1, wherein: the firstportion comprises a primary implant; the surface comprises cementremaining on a bone after removal of the primary implant; anddetermining the representation of the surface comprises identifying thecement in a 3D model.
 6. The method of claim 5, further comprisingcreating a cutting path for removal of the cement.
 7. A system forperforming a procedure, comprising: a first instrument operable toremove a structure from a subject; a second instrument having a distalend operable to contact a surface formed during removal of the structurewith the first instrument; a navigation system operable to: track thesecond instrument at the surface; determine a feature relating to thesurface based on the tracking the second instrument at the surface; andprovide guidance for the procedure based on the feature at the surface.8. The system of claim 7, wherein the feature is a bone defect.
 9. Thesystem of claim 8, wherein the navigation system is configured toprovide the guidance by generating a plan to fill the bone defect. 10.The system of claim 7, wherein the structure comprises a primary implantand the feature comprises cement remaining after removing the primaryimplant from a bone of the subject.
 11. The system of claim 10, whereinthe navigation system is configured to provide the guidance bygenerating a cutting path for removal of the cement.
 12. The system ofclaim 7, wherein the first instrument is a cutting tool and the secondinstrument is a non-cutting probe.
 13. Non-transitory computer-readablemedia storing instructions that, when executed by one or moreprocessors, cause the one or more processors to perform operationscomprising: guiding removal of a first portion of a structure from apatient using a cutting tool; obtaining data relating to a remainingportion of the structure after removal of the first portion; model afeature of the remaining portion of the structure using the data; andguiding a subsequent step of a procedure using the model.
 14. Thenon-transitory computer-readable media of claim 13, wherein guidingremoval of the first portion of the structure from the patient using thecutting tool comprises controlling a robotic device coupled to thecutting tool.
 15. The non-transitory computer-readable media of claim13, wherein the data relating to the remaining portion comprises one ormore images of the remaining portion from a camera.
 16. Thenon-transitory computer-readable media of claim 13, wherein obtainingthe data relating to the remaining portion of the structure comprisestracking a probe as the probe touches a surface of the remaining portionrevealed by removal of the first portion of the structure from thepatient.
 17. The non-transitory computer-readable media of claim 13,wherein the first portion comprises a primary implant.
 18. Thenon-transitory computer-readable media of claim 17, wherein: the featureof the remaining portion comprises cement remaining after removal of theprimary implant from a bone of the patient; and guiding the subsequentstep comprises automatically generating a cutting path for removing thecement from the bone.
 19. The non-transitory computer-readable media ofclaim 13, wherein the feature of the remaining portion is a bone defect.20. The non-transitory computer-readable media of claim 19, whereinguiding the subsequent step comprises automatically generating a planfor filling the bone defect.